does anyone know some or all the places your npc party members interact with each other? For instance, when I have Bastila on Tatooine the other npc speaks to her as we approach the gate to the dune sea. If she isn't there, no one speaks. So I'm guessing all npc's have places where they will interact with whoever else is along. Anyone bothered to figure the trigger spots out?

That's how they work. There's a trigger that launches a dialogue file with all the interactions - banter.dlg - and then that plays out depending on who is present. Because it's a global template there's no way of easily figuring out where they're located. You'd have to look through each module's dynamic info file and see whether the trigger - k_bant_trig.utt - is present. And then extrapolate its location in the game from the coordinates or look in KOTOR Tool's module editor if there's a map for the module.

But off the top of my head, I can think of a few. There's one in the sewers on Taris... just before the rancor, I think. There's one in Davik's estate... I think in his throne room, but frankly every room looks the same to me so I can't be sure. There's another in the Upper City... but again, I forget where it is. There's another on Tatooine just inside the city gates, and another not far outside them, in front of the damaged sandcrawler. There's one on Kashyyyk before the entrance to the Wookiee village. They tend to be in bottleneck areas, near an exit or in a corridor, so that makes them easier to find.